A/T - 1-2 Gear Shift Problem During Cold Weather
88buick20Bulletin: 88-7125-9
Date: Sept. '88
Ref. No.: 88-202-7125
Corp. Ref. No.: 877134
SUBJECT: 1-2 SHIFT DURING COLD WEATHER - SERVICE AND PARTS INFORMATION ON NEW 1-2 ACCUMULATOR PISTON
MODELS AFFECTED: 1988 SKYHAWKS, SKYLARKS, AND CENTURYS EQUIPPED WITH A THM 125C (MD9) TRANSAXLE
FIGURE 2:
BULLETIN COVERS
A new 1-2 Accumulator Piston (421) and Seal (420) for vehicles equipped with a THM 125C transaxle to increase shift consistency during vehicle operation in cold weather conditions. The groove bottom on the 1-2 accumulator piston where the seal is located is flat and the new piston seal is now made of a soft rubber instead of a hard P.T.F.E material (Refer to Figure 2).
Some vehicles equipped with a 1987 THM 125C built between the dates of April 13, 1987, through April 21, 1987 (Julian dates 103-112), may have a rolled or misassembled 1-2 accumulator piston seal, resulting in a possible harsh 1-2 shift. This piston seal has a resemblance to the new (rubber) seal (420). Refer to Bulletin 87-7125-5 for additional information. If replacement of this seal built between April 13, 1987, through April 21, 1987 (Julian dates 103-112) is necessary, the new Accumulator Piston (421) and Seal (420) must be used.
FIGURE 1 - THM 125/125C TRANSAXLE IDENTIFICATION INFORMATION:
DATE OF PRODUCTION CHANGE (Refer to Figure 1)
May 18, 1988 (Julian date 139) the new 1-2 Accumulator Piston and Seal went into production for all Willow Run built THM 125/125C transaxles. Future production changes are scheduled for S.O.P 89 for Windsor built THM 125/125C transaxles.
FIGURE 2:
SERVICE ACTION (Refer to Figure 2)
The new 1-2 Accumulator Piston and Seal can be used on any 1980 through 1988 THM 125C transaxle as a complete assembly. The previous 1-2 Accumulator Piston is no longer available for service use. If replacement of the 1-2 Accumulator Piston seal is necessary, use the following guidelines:
^ The new seal must be used with the new piston.
^ The previous seal must be used with the previous piston.
NOTICE: Do not attempt to mix parts or delayed and extended shift conditions will occur.
SERVICE PARTS INFORMATION
When ordering parts to service the 1-2 Accumulator Assembly, use the following part numbers:
Package No Description
8665920 Package 1-2 Accumulator Piston (421) and Seal (420)
8665807 Seal 1-2 Accumulator (Rubber) (420)
8631895 Seal 1-2 Accumulator (P.T.F.E.)
SERVICE MANUAL REFERENCE
Refer to the THM 125 (MD9) Automatic Transaxle Unit Repair section of your service manual whenever replacement of the 1-2 Accumulator Piston and Seal is necessary.